TECHNICAL FIELD OF THE INVENTION
The present invention relates to a linear motor and an electric injection molding machine using the linear motor.
It has been considered to use a linear motor as a drive source for the injection operation of the electric injection molding machine. For example, the synchronous linear motor 1 shown in FIG. 10 includes a coil assembly 3, a guide member 4 along the coil assembly 3, and a mover 6 including a magnet 5 linearly moving along the guide member 4. The coil assembly 3 is formed in a planar shape by arranging a large number of independent coils 3a at a predetermined pitch in a direction indicated by an arrow A.
The mover 6 of the linear motor 1 can linearly move in the direction of arrow A based on a magnetic field generated when a current is supplied to the coil 3a. Therefore, by connecting the mover 6 to the base of the screw of the injection molding machine and transmitting the linear motion of the mover 6 to the screw, the screw can be moved in the axial direction.
[Problems to be solved by the invention]
In an electric injection molding machine using a conventional linear motor as a drive source, such as the synchronous linear motor 1 described above, heat generation of the coil may be a problem depending on the use condition.
Conventional synchronous linear motors generate heat, such as the need for cooling medium inflow piping and outflow piping for each coil, and the difficulty in ensuring a sufficient contact area between each coil and the cooling medium. The situation was easy to do.
If the use of the injection molding machine is continued in a state in which the coil generates a great deal of heat, the coil may be disconnected or insulation failure may occur. Further, the thrust of the linear motor may decrease due to heat generation, and the magnet may be demagnetized.
In addition, since precision measuring instruments such as linear scales for position measurement are sometimes placed near the linear motor, there is a concern that heat may affect these precision instruments. It is difficult to prevent the occurrence of trouble due to the heat generated by the coil.
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a linear motor capable of preventing troubles due to heat generated by a coil, and an electric injection molding machine using the linear motor.
[Means for Solving the Problems]
A voice coil type linear motor according to the present invention includes a cylindrical coil for generating a magnetic field, a yoke provided along the coil, a magnet relatively movable in an axial direction of the coil, and the coil. Cooling means for cooling. The cooling means cools the yoke and cools the coil, for example, by flowing a liquid or gaseous cooling medium through a coolant passage formed in the yoke.
The voice coil type linear motor referred to in this specification is a cylindrical coil formed by a winding wound in a cylindrical shape, and a yoke (iron) disposed inside or outside the coil along the axial direction of the coil. And a magnet which moves relatively in the axial direction of the coil by a magnetic field generated by the coil. The magnet referred to here is generally a permanent magnet, but may be an electromagnet.
The electric injection molding machine according to the present invention includes a barrel accommodating a screw, and the voice coil linear motor for moving the screw in an axial direction. Cooling means is provided.
In a preferred aspect of the present invention, the apparatus includes a temperature sensor for detecting a temperature of the coil or the cooling medium of the cooling means, and a control device for controlling the cooling medium based on the temperature detected by the temperature sensor. The magnet may be cooled by providing a cooling jacket through which the cooling medium flows. The cooling means may be an electronic cooling device having a Peltier element, a radiation fin, and the like.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The electric injection molding machine 20 shown in FIG. 1 includes an injection device 21 located on the right side in FIG. 1 and a mold clamping device 22 located on the left side in FIG.
The mold clamping device 22 includes a fixed platen 25, a movable platen 26, and a drive mechanism 28 (only a part is shown) for moving the movable platen 26 along the tie bar 27. A fixed mold 30 (shown in FIG. 2) is attached to the fixed platen 25, and a movable mold 31 is attached to the movable platen 26.
As shown in FIG. 2, the injection device 21 is provided on the fixed base 40. The injection device 21 has a slide base 42 that can reciprocate along a guide rail 41 provided on a fixed base 40, and extends in the front-rear direction of the injection molding machine 20 (the axial direction indicated by an arrow X in FIG. 2). You can move.
The injection device 21 includes a frame structure 50, a barrel 51, a voice coil type linear motor 52 functioning as a driving source of the injection operation, a screw rotating mechanism 53, and the like. A screw 54 is housed in the barrel 51. The voice coil type linear motor 52 will be described later in detail.
On the slide base 42, a frame structure 50, a front stand 62 and a rear stand 63 are fixed.
The frame structure 50 includes a first portion 71 that supports the base of the barrel 51, a second portion 72 that is connected to the linear motor 52, and each of the first portion 71 and the second portion 72. It has a pair of left and right connecting walls 73 and 74 connecting both sides, a bottom wall 75, and the like. The first and second portions 71 and 72, the connecting walls 73 and 74, and the bottom wall 75 are formed by casting. They are integrally formed with each other, and are configured in a box shape with a bottom as a whole.
The voice coil type linear motor 52 includes a fixed side member 81 including a plurality of electromagnetic coils 80 provided in parallel between the stands 62 and 63 and a permanent magnet driven in the X direction by a magnetic field generated by the coil 80. A movable member 83 including a magnet 82 is provided.
The movable member 83 of the linear motor 52 can reciprocate between the stands 62 and 63 along a guide member 84 provided on the slide base 42. An output shaft 86 is connected to a connection plate 85 that is a part of the movable member 83.
Each coil 80 of the voice coil type linear motor 52 is formed in a cylindrical shape by winding a conducting wire 80a as schematically shown in FIG. 4, and an iron core (yoke 87) is provided inside the coil 80. I have. A magnet 82 is provided on the outer peripheral side of the coil 80. The movable member 83 including the magnet 82 relatively moves in the direction of the axis C of the coil 80 based on a magnetic field generated when a current is supplied to the coil 80.
The coil 80 is connected to a current supply device 89 via a power cable 80b. In order to prevent disconnection of the conductive cable 80b, it is desirable to set the coil 80 to the fixed side and the magnet 82 to the movable side as in this embodiment. However, if measures are taken so that the conductive cable 80b can move without difficulty, The coil 80 and the yoke 87 may be on the moving side, and the magnet 82 may be on the fixed side.
Note that a magnet may be provided inside the coil 80 and a yoke may be provided outside the coil 80. Further, the coil 80 may be a rectangular tube. The shape and the like of the magnet 82 are also arbitrary, and an appropriate shape may be used as needed. This linear motor 52 is a direct current type linear motor.
In the vicinity of the base of the barrel 51, a hopper 88 for supplying a resin that is a material of an injection molded product is provided. The hopper 88 is attached to the first portion 71 of the frame structure 50. The barrel 51 is provided with a heater (not shown) for heating and melting the resin.
The screw rotation mechanism 53 includes a shaft 90 to which the screw 54 is connected, a sleeve member 91 fitted to the shaft 90, a motor 92 for rotating the sleeve member 91, a first bearing 93, The bearing unit 94 is included.
More specifically, as schematically shown in FIG. 3, a spline portion 95 is formed on the outer periphery of the shaft 90 along the axial direction. By fitting the sleeve member 91 to the spline portion 95, the shaft 90 can be moved relative to the sleeve member 91 in the axial direction, and the shaft 90 and the sleeve member 91 can be integrally rotated. It has become.
The sleeve member 91 is rotatably supported on the intermediate support wall 100 by the first bearing portion 93. The intermediate support wall 100 is fixed to the bottom wall 75 of the frame structure 50.
A motor support 101 is provided above the frame structure 50, and the motor 92 is mounted on the motor support 101. A power transmission member 105 such as a belt is wound between a driving pulley 103 attached to the output shaft 102 of the motor 92 and a driven pulley 104 attached to the sleeve member 91. Therefore, by rotating the output shaft 102 of the motor 92, the sleeve member 91 can be rotated. When the sleeve member 91 rotates, the shaft 90 fitted to the spline portion 95 rotates, so that the screw 54 rotates.
The rear end of the shaft 90 is connected to an output shaft 86 of the linear motor 52 by a connecting mechanism 106 having a second bearing 94. The connecting mechanism 106 connects the output shaft 86 and the shaft 90 to each other, and allows relative movement of the two in the rotation direction. That is, the linear motion of the output shaft 86 in the axial direction can be transmitted to the shaft 90, and the rotational motion of the shaft 90 is not transmitted to the output shaft 86.
The nozzle 110 formed at the tip of the barrel 51 is located on the center line of the hole 111 formed in the fixed platen 25. The fixed platen 25 and the frame structure 50 are connected to each other by, for example, a ball screw 115 and a nozzle touch mechanism 116 using a servomotor or the like.
By driving the nozzle touch mechanism 116, the injection device 21 can be moved forward and backward with respect to the fixed platen 25 along the guide rail 41. When the injection device 21 is advanced to a predetermined position, the tip of the nozzle 110 is in contact with the injection port 30a of the fixed mold 30.
As shown in FIGS. 5 to 7, the voice coil type linear motor 52 has refrigerant passages 120 and 121 formed in the yoke 87 as a cooling unit of the coil 80. Since the heat generated by the coil 80 acts on the outer peripheral side of the yoke 87, in order to enhance the cooling efficiency, a refrigerant flow path 120 on the inflow side is formed on the outer peripheral side of the yoke 87. A coolant channel 121 is formed.
These refrigerant channels 120 and 121 are connected to a cooling device 123 via a refrigerant pipe 122. The refrigerant passages 120 and 121, the refrigerant pipe 122, the cooling device 123, and the like constitute a cooling means according to the present invention. The cooling medium is not limited to a liquid, but may be a gas or a gas-liquid mixture. The refrigerant flow path 120 on the inflow side shown in FIG. 7 has a larger flow cross-sectional area than the refrigerant flow path 121 on the return side, but the cross-sectional area of each of the refrigerant flow paths 120 and 121 may be the same. .
As shown in FIG. 5, a temperature sensor 130 is provided to detect the temperature of the coil 80. A signal related to the temperature detected by the temperature sensor 130 is output to the control device 131. The control device 131 controls the cooling device 123 so that the temperature of the cooling medium is maintained in a preset range. That is, the temperature near the coil 80 is measured by the temperature sensor 130, and the cooling device 123 is managed. Note that, instead of detecting the temperature near the coil 80, the temperature of the coil 80 may be estimated by detecting the temperature of the cooling medium.
Inside the yoke 87, the cooling medium flows in the directions indicated by arrows Q1 and Q2 in FIG. The temperature of the cooling medium is controlled by the cooling device 123, and the cooling medium whose temperature is controlled flows through the coolant passages 120 and 121, whereby the coil 80 is actively cooled, and the coil 80 and its surroundings have a substantially constant temperature. Can be kept.
Further, by providing a sensor for monitoring the temperature of the cooling medium, it is possible to detect an abnormality of the injection molding machine 20. When an abnormality is detected, an alarm (alarm) can be issued to the control system of the injection molding machine 20 or the operation of the injection molding machine 20 can be stopped.
Next, the operation of the injection molding machine 20 having the above configuration will be described.
The dies 30 and 31 are closed by the mold clamping device 22, and the injection device 21 is advanced toward the fixed platen 25 by the nozzle touch mechanism 116 so that the tip of the nozzle 110 abuts the injection port 30 a of the fixed mold 30. Let it.
Then, by supplying a current to the coil 80 of the linear motor 52, the movable member 83 of the linear motor 52 is moved forward as schematically shown in FIG. When the movable-side member 83 advances, the shaft 90 advances via the output shaft 86, and further the screw 54 advances, so that the molten resin previously measured in the barrel 51 is displaced from the tip of the nozzle 110 by the screw 54. It is extruded and filled in the molds 30 and 31.
After the resin injected into the molds 30 and 31 is cooled, the movable member 83 of the linear motor 52 is retracted, whereby the screw 54 is retracted by a predetermined amount. Further, by rotating the shaft 90 by the motor 92, the screw 54 is rotated, and the molten resin is kneaded while being fed to the tip end side of the barrel 51, and the molten resin is measured. Then, the molds 30 and 31 are opened, and the molded product is ejected by the ejector mechanism, thereby completing one cycle of the injection molding process.
In the injection molding machine 20, since the frame structure 50 is a box-shaped integrally molded product (for example, a cast product), the injection molding machine 20 has a large resistance to a tensile load in the front-rear direction, as well as in the vertical and horizontal directions. High rigidity can be exhibited. For this reason, even if the screw 54 performs a linear motion at high speed by the linear motor 52, it is possible to suppress the frame structure 50 from being vibrated or deformed.
Further, a motor 92 for screw rotation is fixed to a motor support portion 101 provided on the frame structure 50 having high rigidity, and a shaft 90 and a sleeve member 91 are fitted to each other via a spline portion 95. . According to this structure, when the screw 54 is linearly moved in the axial direction by the linear motor 52, the motor 92 itself stops on the motor support portion 101 without linearly moving. For this reason, the movable side mass (inertial mass) that linearly moves integrally with the screw 54 can be reduced, and the linear reciprocating motion by the linear motor 52 can be further accelerated.
For the above reasons, it is possible to further reduce the cycle time required for injection molding. In addition, since the integral frame structure 50 formed by casting or the like is employed, the number of components constituting the frame structure 50 can be reduced.
In the voice coil linear motor 52 of this embodiment, the temperature of the cooling medium flowing inside the coil 80 is controlled by the cooling device 123, and the temperature-controlled cooling medium flows through the refrigerant flow paths 120 and 121, so that the coil medium is cooled. 80 is cooled and coil 80 and its surroundings are maintained at a substantially constant desired temperature. Thereby, it is possible to prevent troubles such as disconnection or reduction of thrust due to overheating of the coil 80 and demagnetization of the magnet 82.
Further, by suppressing the temperature rise of the coil 80, the temperature rise in the vicinity of the coil 80 can also be suppressed, and as a result, the effect of high temperature on various devices disposed in the vicinity of the coil 80 can be avoided. .
FIG. 8 shows a voice coil type linear motor 52 'in an injection molding machine according to a second embodiment of the present invention. In the voice coil type linear motor 52 ′, by providing the cooling jacket 140 on the inner surface side of the magnet 82, the magnet 82 affected by the heat generated by the coil 80 can also be cooled.
The refrigerant pipe 141 is connected to the cooling jacket 140, and the cooling medium cooled by the cooling device 123 flows through the refrigerant channel 142 of the cooling jacket 140, so that the magnets 82 are actively cooled. In other respects, the configuration and operation of the second embodiment are the same as those of the injection device 21 of the first embodiment. I do.
FIG. 9 shows a voice coil type linear motor 52 in an injection molding machine according to a third embodiment of the present invention. This voice coil type linear motor 52 includes an electronic cooling device 200. The electronic cooling device 200 includes a Peltier element 201 having a Peltier effect, a radiation fin 202 for cooling the Peltier element 201, a controller 203 for controlling a DC current supplied to the Peltier element 201, and the like.
The surface on the low temperature side of each Peltier element 201 is attached to the magnet 82 and the yoke 87, respectively. The radiating fins 202 are provided on the surface on the high temperature side of each Peltier element 201. When a current is supplied from the DC power supply 204 to these Peltier elements 201, the magnet 82 and the yoke 87 are cooled by the Peltier effect. By controlling this current by the controller 203, the temperature of the voice coil linear motor 52 can be controlled. Other configurations and operations are the same as those of the injection device 21 of the first embodiment in the third embodiment. Therefore, common portions are denoted by common reference numerals, and description thereof is omitted. I do.
In carrying out the present invention, it goes without saying that the components of the present invention such as the voice coil type linear motor can be variously modified without departing from the gist of the present invention. Further, the present invention can be applied to an injection molding machine for synthetic resin products, and can also be applied to an injection molding machine for metal products.
【The invention's effect】
According to the voice coil type linear motor described in the first aspect, it is possible to prevent a problem caused by overheating of the coil.
According to the electric injection molding machine described in the second aspect, it is possible to prevent a problem from occurring due to heat generation of the voice coil type linear motor.
According to the invention described in claim 3, the cooling medium can be controlled according to the heat generation state of the coil, and overheating of the coil and the like can be more effectively prevented.
According to the invention described in claim 4, the magnet side can also be cooled, and the influence of heat generation of the coil can be prevented from affecting the magnet.
In the present invention, when an electronic cooling device having a Peltier element and a radiating fin is adopted as the cooling means, the temperature control of the linear motor can be performed electrically, so that the temperature control is easy, and the cooling medium It is possible to configure the cooling device more compactly than in the case of using.
[Brief description of the drawings]
FIG. 1 is a perspective view of an electric injection molding machine showing a first embodiment of the present invention.
FIG. 2 is a sectional view taken along the axial direction of a part of the injection molding machine shown in FIG.
FIG. 3 is a cross-sectional view schematically showing a state in which a screw of the injection molding machine shown in FIG. 1 has advanced.
FIG. 4 is a perspective view schematically showing a part of a voice coil type linear motor.
FIG. 5 is a sectional view showing a voice coil type linear motor and a cooling device of the injection molding machine shown in FIG. 1;
FIG. 6 is a sectional view of a yoke of the voice coil linear motor shown in FIG. 5;
FIG. 7 is a sectional view of the yoke taken along line F7-F7 in FIG. 6;
FIG. 8 is a sectional view showing a linear motor and a cooling device of an electric injection molding machine according to a second embodiment of the present invention.
FIG. 9 is a sectional view showing a linear motor and an electronic cooling device of an electric injection molding machine according to a third embodiment of the present invention.
FIG. 10 is a perspective view of a conventional synchronous linear motor.
[Explanation of symbols]
Reference Signs List 20 electric injection molding machine 51 barrel 52 voice coil type linear motor 54 screw 80 coil 82 magnet 87 yoke 120, 121 refrigerant channel 123 cooling device 130 temperature sensor 131 control device 140 cooling Jacket 200 Electronic cooling device 201 Peltier element 202 Radiating fin